How do parents, primary care physicians (PCPs), and specialists (endocrinologists) make decisions to treat short children (idiopathic short stature; ISS) with growth hormone (GH)? Decisions about GH use will affect up to 2 million children, with potential costs of up to $40 billion per year. Building on our previous work, we identify a set of 4 decisions that, together, govern GH use: whether to discuss the child's growth, refer the child to an endocrinologist, initiate GH treatment, and continue GH. Using Judgment Analysis, we hypothesize that 5 domains will influence these key decisions; the domains are physiological characteristics, attitudes and beliefs, structural and organizational factors, knowledge and experience, and sociodemographic factors. In Aim 1, we are concerned with decisions actually made by families and their PCPs about whether to discuss and action about growth in children whose heights are below the 10th percentile for age. The methods for Aim 1 involve analyses of actual decisions made for short children in primary care (n=534), using data from 3 sources: interviews with parents and PCPs, chart review, and standardized questionnaires. Qualitative and quantitative analyses be performed. In Aim 2, we focus on referrals by PCPs to endocrinologists. We conduct a national study of a stratified sample of PCPs (n = 1920) to define the determinants of decisions to refer short children to endocrinologists, using surveys with factorial experimental design. Findings from Aim 1 will help to structure the Aim 2 survey. In Aim 3, we focus on endocrinologists' decisions about whether to initiate and whether to continue GH (as individualized therapeutic trials). We conduct a national study of a census of pediatric endocrinologists (n= 1200) to define the determinants of their recommendations for initiation and continuation/discontinuation of GH in ISS, using case scenarios factorial experimental design. We also examine a longitudinal database to assess duration of GH treatment in individual children. In all 3 aims, we will obtain information on the 5 domains for decision-makers and assess their explanatory power for the judgments under study. This project will provide fundamental knowledge about how decisions are made that determine GH use. It will identify key drivers of GH use, and define pivotal points at which GH use can be modulated. It will provide a foundation future prospective, longitudinal studies of short stature- including interventions that can help families and physicians make informed management decisions. Moreover, the knowledge gained on determinants of treatment use will likely be applicable to many emerging therapies that have ambiguous beginnings and endings, but are highly valued by patients.